1. Field of the Invention
The present invention relates to a magnetic recording medium and a head slider.
2. Description of the Related Art
In a magnetic recording device that is generally widely used as an external storing unit for computers and other various information terminals, a head slider equipped with a recording transducer (also simply referred to as “head” in the present invention) reads and writes information, while flying (or floating) over a magnetic recording medium (also simply referred to as “medium” in the present invention) such as a hard disc.
The distance between the head and a magnetic layer that records (writes) and/or reproduces (reads) magnetic information on the hard disk, is called a magnetic spacing. The smaller the magnetic spacing is, the more improved the recording density is. Accordingly, the present level of the head floating gap has become as small as 10 nm or less as a result of a strong need for higher recording density in recent years. In such an ultra-small floating gap, only a small amount of contaminants adhered onto a head slider may make the flying stability (or floating stability) of the head greatly out of balance.
Volatile organic materials, debris, etc. brought about from the environment are examples of such contaminants. As the head slider moves, volatile organic materials, debris, etc. adhered to the hard disk are scraped together and collected on the head slider, and eventually fill in the head floating gap, resulting in head crashing.
Furthermore, it is known that the lubricant is transferred from the surface of the medium to the head slider surface side by means of evaporation from the medium and intermittent contact with the head slider, etc., with the result that a film as thick as the lubricant layer on the medium is formed inevitably on the outermost head slider surface facing the medium (also referred to as “ABS” that is an abbreviation of “air bearing surface”).
In a device having a sufficiently wide floating gap, that is, a device with a low recording density, such lubricants adhered to the ABS have been posing little problem. However, as the floating gap has been made very small as in the devices at the present day, such a behavior has come to be on the level that cannot be ignored as a factor for making the flying of the head unstable. It is understood that the instability of the flying is caused by the lubricant on the ABS contacting with the lubricant of the medium, and forming a liquid bridge.
As a method to solve the above-described problem, it is proposed to install a lubricant layer made of a water-repellent resin having an average film thickness of 1.5 nm or less on the surface of a head slider protective layer that faces the magnetic recording medium, so as to decrease the surface tension of the head slider surface (Japanese Patent Application No. 16-156468). It is to be noted that carbon-type materials such as amorphous carbon are considered to be desirable for the head slider protective layer from the viewpoint of heat resistance, corrosion resistance and abrasion resistance, and carbon-type protective layers deposited by the sputtering method and the CVD (Chemical Vapor Deposition) method are used in general.
One distinguished feature of such a method is that the lubricant applied onto the head slider is subjected to a UV (ultraviolet) irradiation treatment so that the lubricant layer is transformed from a liquid-like state in which it is easily deformed and mobilized into a state in which it is hard to be deformed and mobilized, and also it is tightly adhered to the head slider surface. Using this head slider, not only is the adhesion of contaminants decreased, but also it is hard for the liquid bridge to be formed with the lubricant applied to the magnetic recording medium.
It is thought that the effect of the above-described UV ray irradiation is brought about by the progress of chemical bonding between the lubricant and the head slider protective layer which is caused by activated points in the lubricant formed by photoelectrons excited in and emitted from the head slider protective layer.
However, amorphous carbons widely used as materials for the present protective layer, have a low photoelectron emission efficiency, since their ionization potential is as high as about 5.8 eV. Accordingly, a long UV irradiation process is necessary so as to acquire a sufficient force of adhesion. Such long UV irradiation will accelerate the decomposition of the lubricant, causing thinning of the film and deterioration of the adhesion force that is considered to be due to the lowering of the molecular weight, with the result that there occur problems such as deterioration of the adhesion rate of the lubricant to the head slider surface, and degradation of the adhesion uniformity that accompanies the adhesion rate deterioration.
While the above explanation is made on a head slider, similar technologies can be also applied to the lubricant layer on a magnetic recording medium, and therefore, there are similar problems. Although technologies such as one in which an adhesion force reinforcing substance interposed in between is adhered to the protective layer surface, are disclosed regarding the magnetic recording medium protective layer (Japanese Unexamined Patent Application Publication No. 03-25723, for example), they are still insufficient.
It is an object of the present invention to solve such problems and provide a magnetic recording medium and a head slider that can furnish excellent head flying stability, as well as a magnetic recording device having a head with an excellent head flying stability. It is another object of the present invention to provide a method for manufacturing a magnetic recording medium and a head slider that can furnish excellent head flying stability in a short time. Other objects and advantages of the present invention will be clarified through the following explanation.